Villains from Science-Fiction (Sci-Fi for short) genre works - science-fiction is based on scientifically-possible worlds or settings without the use of fantastical elements such as magic or the supernatural : however as the genre evolved it grew many subgenres and sometimes the line between science-fiction and fantasy blurred.. thus there is "hard" sci-fi (which focuses on the scientifically probable), "soft" sci-fi (which employs less probable or outdated scientific themes) and science-fantasy (in which science is merged with fantasy, often to the point is is considered a twin-genre of *both* science fiction and fantasy).

Sometimes works that began as theoretical stories (sci-fi) become science-fantasy over time as knowledge of science increases : this is especially true of early works from 1950s, 60s or earlier - where they incorporate fantastical ideas that at the time were seen as plausible but in modern times are resigned purely to fantasy of psuedo-science.